Is he at the age to be looking for a mate?<<<
No, he is only about 4 months old and is am easily spooked cat, always runs from sounds and new people, he wanted to go out and finally managed to do so.
Maybe he knew he would be hungry again, for he insisted on wet and dry food at all times.
I still call him, but haven’t heard him or felt like he was close.
Oh, I’m so sorry. I know you miss the little furball. I had a cat come home unexpectedly once after about 10 days. She just showed up like nothing was new - after I combed the shelters, all the bushes, all around where we lived. Those cats - they have minds of their own. I hope he comes home soon, though.